Growth Factor Modulation of Fibroblast Proliferation,Differentiation, and Invasion: Implications for Tissue Valve Engineering

摘要

We have previously shown that transforming growth factor-betal (TGF-pl) stimulates trans-differentiation of fibroblasts into smooth muscle a-actin (alpha-SMA) positive myofibroblasts. However, TGF-p, as such, is unsuitable for effective population of a heart valve matrix, because it dose-dependently inhibits growth of fibroblasts. The aim of this study was to investigate combinations of other growth factors with TGF-p to stimulate the proliferation of suitably differentiated cells and to enhance their invasion into aortic valve matrices. Human dermal mesenchymal cells (hDMCl.l) were treated with combinations of growth factors to stimulate these cells to trans-differentiate into myofibroblasts, to proliferate, and to invade. Growth factors were chosen after expression of their respective receptors was confirmed in hDMCl.l using reverse transcriptase polymerase chain reaction. We combined TGF-P with several growth factors such as insulin-like growth factor (IGF-1, IGF-2), epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), and platelet-derived growth factor (PDGF-AA, PDGF-BB, and PDGF-AB). Nuclear Ki67 staining, MTT assay, and cell counting revealed that only EGF and bFGF were capable of overcoming TGF-p-induced growth inhibition. However, bFGF but not EGF inhibited TGF-p-induced alpha-SMA expression, as evidenced by immuno-cytochemistry and Western blotting. A growth factor cocktail (TGF-beta, EGF, bFGF) has been established that maintains TGF-P-induced trans-differentiation but overcomes TGF-p-induced growth inhibition while stimulating fibroblast proliferation and invasion.